In-situ forming biodegradable glycol chitosan-based hydrogels: Synthesis, characterization, and chondrocyte culture

In-situ forming hydrogels from thiolated glycol chitosan (GCH-SH) and vinyl sulfone-modified PEG (PL-VS) were designed, prepared and successfully applied as biodegradable, non-toxic bio-scaffolds for chondrocyte culture. The hydrogels could be formed in situ under physiological conditions via Michael-type addition between the GCH-SH and PL-VS at a low polymer concentration of 1-3% (w/v). Gelation times varied from 0.75 to 50min, depending on the polymer concentration and the arm number of PEG-VS. Moreover, a high arm number and a high polymer concentration may lead to efficient network formation of GCH-SH/PEG-VS hydrogels. These hydrogels were found biodegradable in the presence of lysozyme, a cationic protein in the body, for a long period of time. Rheological studies indicated that these hydrogels generally displayed highly elastic property and had higher mechanical strength than those from thiolated hyaluronic acid/PEG-VS reported previously. SEM observation revealed that these hydrogels possessed well-interconnected microporous morphology. Besides these, the chondrocytes could be incorporated and homogeneously distributed in the hydrogel based on GCH-SH and 4-arm PL-VS. Importantly, after cell culture of 14days, the chondrocytes in the hydrogel remained viable, as determined by a live-dead assay, and the cells kept their round chondrocytic phenotype. These results suggest that Michael-type addition is an effective method in the preparation of in-situ forming, biodegradable GCH-based hydrogels serving as bio-scaffolds for chondrocyte culture.